Investigation of Microscopic Nonmetallic Inclusions in Powder Metallurgical High-Speed Steels

This study focuses on the application and comparison of advanced analytical methods for investigating nonmetallic inclusions (NMIs) in powder metallurgical (PM) high-speed steels based on the standards HS6-5-3C and HS10-2-5-8. Automated and manual scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS) are employed to analyze the size, distribution, and chemical composition of NMIs. Classical statistical approaches are complemented by the generalized Pareto distribution (GPD) method, enabling the estimation of the largest inclusion size within a defined volume. Thermodynamic evaluations, based on SEM/EDS data and supported by Factsage databases, are utilized to determine the equilibrium phase composition of inclusions. The study highlights the integration of these methodologies, demonstrating their ability to provide a comprehensive assessment of steel cleanness for different sample conditions. The GPD method proves effective in estimating extreme inclusion sizes, while thermodynamic tools offer insights into phase distributions and chemical variability. This methodological framework establishes a robust foundation for future metallurgical research, particularly in understanding the relationship between NMIs and steel properties.